/*
 * Copyright 2002-2014 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package qunar.tc.bistoury.instrument.client.spring.el;

import java.math.BigDecimal;
import java.math.BigInteger;

/**
 * A simple basic {@link TypeComparator} implementation.
 * It supports comparison of Numbers and types implementing Comparable.
 *
 * @author Andy Clement
 * @author Juergen Hoeller
 * @author Giovanni Dall'Oglio Risso
 * @since 3.0
 */
class StandardTypeComparator implements TypeComparator {

    @Override
    public boolean canCompare(Object left, Object right) {
        if (left == null || right == null) {
            return true;
        }
        if (left instanceof Number && right instanceof Number) {
            return true;
        }
        if (left instanceof Comparable) {
            return true;
        }
        return false;
    }

    @Override
    @SuppressWarnings("unchecked")
    public int compare(Object left, Object right) throws SpelEvaluationException {
        // If one is null, check if the other is
        if (left == null) {
            return (right == null ? 0 : -1);
        } else if (right == null) {
            return 1;  // left cannot be null at this point
        }

        // Basic number comparisons
        if (left instanceof Number && right instanceof Number) {
            Number leftNumber = (Number) left;
            Number rightNumber = (Number) right;

            if (leftNumber instanceof BigDecimal || rightNumber instanceof BigDecimal) {
                BigDecimal leftBigDecimal = NumberUtils.convertNumberToTargetClass(leftNumber, BigDecimal.class);
                BigDecimal rightBigDecimal = NumberUtils.convertNumberToTargetClass(rightNumber, BigDecimal.class);
                return leftBigDecimal.compareTo(rightBigDecimal);
            } else if (leftNumber instanceof Double || rightNumber instanceof Double) {
                return Double.compare(leftNumber.doubleValue(), rightNumber.doubleValue());
            } else if (leftNumber instanceof Float || rightNumber instanceof Float) {
                return Float.compare(leftNumber.floatValue(), rightNumber.floatValue());
            } else if (leftNumber instanceof BigInteger || rightNumber instanceof BigInteger) {
                BigInteger leftBigInteger = NumberUtils.convertNumberToTargetClass(leftNumber, BigInteger.class);
                BigInteger rightBigInteger = NumberUtils.convertNumberToTargetClass(rightNumber, BigInteger.class);
                return leftBigInteger.compareTo(rightBigInteger);
            } else if (leftNumber instanceof Long || rightNumber instanceof Long) {
                // Don't call Long.compare here - only available on JDK 1.7+
                return compare(leftNumber.longValue(), rightNumber.longValue());
            } else if (leftNumber instanceof Integer || rightNumber instanceof Integer) {
                // Don't call Integer.compare here - only available on JDK 1.7+
                return compare(leftNumber.intValue(), rightNumber.intValue());
            } else if (leftNumber instanceof Short || rightNumber instanceof Short) {
                // Don't call Short.compare here - only available on JDK 1.7+
                return compare(leftNumber.shortValue(), rightNumber.shortValue());
            } else if (leftNumber instanceof Byte || rightNumber instanceof Byte) {
                // Don't call Short.compare here - only available on JDK 1.7+
                return compare(leftNumber.byteValue(), rightNumber.byteValue());
            } else {
                // Unknown Number subtypes -> best guess is double multiplication
                return Double.compare(leftNumber.doubleValue(), rightNumber.doubleValue());
            }
        }

        try {
            if (left instanceof Comparable) {
                return ((Comparable<Object>) left).compareTo(right);
            }
        } catch (ClassCastException ex) {
            throw new SpelEvaluationException(ex, SpelMessage.NOT_COMPARABLE, left.getClass(), right.getClass());
        }

        throw new SpelEvaluationException(SpelMessage.NOT_COMPARABLE, left.getClass(), right.getClass());
    }


    private static int compare(long x, long y) {
        return (x < y ? -1 : (x > y ? 1 : 0));
    }

    private static int compare(int x, int y) {
        return (x < y ? -1 : (x > y ? 1 : 0));
    }

    private static int compare(short x, short y) {
        return x - y;
    }

    private static int compare(byte x, byte y) {
        return x - y;
    }

}
